The present invention is related to the field of partially or fully automatic synthesis of art pieces by computer executed methods such as the synthesis of digital reliefs, the synthesis of sculptures, and, more specifically, to methods for the synthesis of bas-reliefs and of high reliefs.
In the present disclosure, non-patent publications are cited by a number, e.g. [1], which refers to the publications listed in section “Cited non-Patent Publications” at the end of the description.
We disclose a system for generating by computer pieces of art that are partly sculpture and partly image, incorporating visually smooth transitions between 3D scene objects and their flat representations. We provide new means of expression combining within a same composition 2D and 3D scene elements. An observer looking at the final printed 2D-3D artwork resulting from such a composition cannot easily distinguish the 2D part and the 3D part.
Automatic generation of artwork by computer executed methods has been a significant research and development topic. The goal of some of these works is either to create tools for the artists or to generate artworks in a completely automated manner. Our invention is related to the domain of relief generation. Relief synthesis is a sculptural technique where the sculpted elements are attached to a background surface (e.g. relief plane). There are different types of reliefs depending on the attachment type of the sculpted part. If the sculpted parts are designed only as tiny elevations from the surface without undercuts, the relief is called bas-relief (or low-relief). If parts detach from the surface as 3D shapes, the relief is called high relief.
The main approach for designing a bas-relief is based on a height-field [1]. For a given camera position, the input scene is captured as a height-field (also called depth field). This then defines the elevation ranges on a regular mesh grid. The main challenge of the bas-relief methods consists in mapping the height-field of the scene to a limited range of elevations while preserving the details of the original scene. Initial methods use non-linear compression operations. However, they cannot generate plausible reliefs for higher depth range variations. Recent methods [2, 3] use the gradient domain to compress the height field. These methods preserve many details of the scene at very limited height ranges.
For the high relief, the height field representation of the bas-relief is not applicable. Instead, the 3D scene geometry should be directly connected with the relief plane. Schüller et al. [4] introduce a generalization of bas-relief synthesis for arbitrary target surfaces. Since this method does not require a height field as input data but uses the 3D scene geometry, it can also be used to generate high reliefs. A recent work by Arpa et al. [5] creates high reliefs that can be viewed from a wide range of viewing angles with an appearance similar to the original 3D shape. Well-chosen control points enable attaching the scene to the relief plane.
Our invention has similarities to high reliefs. However, the challenges are different. Although, in both, the 3D parts are attached to a plane, in high reliefs there is no smooth transition between the planar projected elements and the 3D elements. All forms are in 3D within a limited space. In the present invention, since some parts of the scene are projected onto the rendering plane, the method of attachment aims at ensuring a seamless continuity between 2D and 3D regions of a scene. Such a seamless continuity is achieved with the addition of relief profiles and with smoothing operations relying on optimization.
Artists who blend a painting and a sculpture manually must meet several challenges. First, the geometric visual information of a painting does not fundamentally change as a function of the viewing position while a sculpture reveals new information at each viewing angle. In sculpture paintings, each new viewing position creates a new composition of 2D and 3D scene elements. Creating a composition that provides plausible percepts for many different viewing angles is challenging. In addition, the textures of the 2D and 3D parts need to be blended. Lighting can dramatically change the perception of the 3D elements. Depending on the type of light and its position, the diffuse shading, specular highlights, and shadows can change to a great extent the appearance of the 3D elements. Contradictions with the 2D part may arise.
The present invention discloses methods to synthesize by computation a piece of art where 2D and 3D parts of some salient scene objects are smoothly integrated.